Population structure of Chrysoporthe austroafricana in southern Africa determined using Vegetative Compatibility Groups (VCGs)

Chrysoporthe austroafricana is one of the most damaging pathogens of Eucalyptus trees in southern Africa. It also occurs on non-native Tibouchina granulosa trees and native Syzygium species. Additional isolates of the pathogen from previously unstudied countries in the region have become available from survey studies. The aim of this study was to use VCGs to consider the diversity in populations of isolates collected in various countries in southern Africa (Malawi, Mozambique, Namibia, South Africa and Zambia) and from different hosts. We also wanted to determine whether there are shared VCGs among these countries and hosts in southern Africa and establish a VCG tester strain data base. Results showed a high diversity amongst isolates from different countries and hosts, but suggested little movement of VCGs among countries or hosts based on the available isolates. A total of 108 VCG tester strains were identified for southern Africa.The University of Pretoria (UP), National Research Foundation (NRF), Forestry and Agricultural Biotechnology Institute (FABI) and Tree Protection Cooperative Program (TPCP).http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1439-0329hb2016Microbiology and Plant Patholog

Species delineation in the tree pathogen genus Celoporthe (Cryphonectriaceae) in southern Africa

The genus Celoporthe was first described when C. dispersa was discovered in South Africa associated with dieback and cankers on trees in the Myrtales. Four additional species were recently described from Eucalyptus and Syzygium cumini in China as well as S. aromaticum and Eucalyptus in Indonesia. Inoculation trials have shown that all Celoporthe species, including those that have not been found on Eucalyptus species in nature, are pathogenic to Eucalyptus and they are thus potentially threatening to commercial Eucalyptus forestry. New isolates, morphologically similar to Celoporthe, have been collected from S. legatti in South Africa and S. guineense in Zambia. Multigene phylogenetic analyses based on DNA sequences of the ITS region, TEF1a gene and two areas of the b-tubulin gene revealed additional cryptic species in Celoporthe. Phylogenetic data were supported by morphological differences. These resulted in the description of two previously unknown species of Celoporthe, namely C. fontana and C. woodiana, for two of these cryptic groups, while the third group represented C. dispersa. These species all can readily infect Eucalyptus as well as several species of Syzygium, the latter of which are native to Africa.We thank the University of Pretoria (UP), National Research Foundation (NRF), Forestry and Agricultural Biotechnology Institute (FABI) and Tree Protection Cooperative Program (TPCP) for financial support.http://www.mycologia.org/am201

Diversity and host range of the Cryphonectriaceae in southern Africa

The Cryphonectriaceae is a recently established family in the Diaporthales and includes important tree pathogens. Four genera occur in Africa, namely Aurifilum, Celoporthe, Chrysoporthe and Holocryphia and are known tree pathogens able to infect native trees, non-native ornamentals and forestry trees in the Myrtales. In Chapter One of this thesis, the taxonomic history, pathology, possible origins, host range, distribution, symptoms, impact and possible control of Cryphonectriaceae in Africa was considered. This review aimed to provide a background for the study of specimens resembling Cryphonectriaceae collected from southern Africa during surveys throughout 2005-2009. Furthermore, it provided a background for the study of the population diversity of Chr. austroafricana in southern Africa and its possible movement within the country and between known hosts. Although great progress has been made in studying the Cryphonectriaceae it is clear that our knowledge of these pathogens in Africa remain limited, despite evidence that the centers of origin of some of them are most likely in Africa. Chapter Two reported, for the first time, Chr. austroafricana from Namibia as well as areas in South Africa, outside of its previously known range. Holocryphia eucalypti was reported from Swaziland and the host and distribution range of Celoporthe species are now known to include S. legatti in the Soutpansberg area in South Africa and S. cordatum in Zambia. Latruncellus aurora gen. sp. nov. was discovered on Galpinia transvaalica (Lythraceae, Myrtales) in Swaziland, representing the first report of a member of the Cryphonectriaceae infecting Lythraceae in Africa. In Chapter Three of this thesis the diversity of Chr. austroafricana was assessed based on Vegetative Compatibility Groupings (VCGs). A high diversity was observed for Chr. austroafricana in southern Africa, with very limited movement of VCGs between different locations and hosts. This high VCG diversity is indicative of a native pathogen, confirming previous hypotheses in this regard. This study provides a VCG tester database that will allow assignment of newly discovered isolates to a specific VCG grouping and allowing more rapid identification of new introductions. This technique is especially valuable in that it is cheap and easy to apply, allowing for all laboratories in Africa to be able to use it. Two previously unknown Celoporthe species were described in Chapter Four. These are Cel. fontana, described from S. cordatum in Zambia, and Cel. woodiana from T. granulosa in South Africa. This chapter relied strongly on the phylogenetic species concept (PSC) to recognize these new species. The PSC is especially helpful in a genus such as Celoporthe where limited specimens are available for morphological comparisons and where morphological differences are difficult to identify. This thesis greatly expanded our knowledge on the diversity, distribution and host range of the Cryphonectriaceae in southern Africa and described a novel genus and three novel species. Based on pathogenicity tests all three new species have the potential to cause disease on Eucalyptus, a tree of importance in forestry in various southern African countries, indicating that in the future these fungi could emerge as important pathogens of Eucalyptus species in Africa and other continents.Dissertation (MSc)--University of Pretoria, 2012.Microbiology and Plant PathologyMScUnrestricte

New records of the Cryphonectriaceae from southern Africa including Latruncellus aurorae gen. sp. nov.

The Cryphonectriaceae accommodates some of the world’s most important tree pathogens, including four genera known from native and introduced Myrtales in Africa. Surveys in the past 3 y in southern Africa have led to the discovery of cankers with fruiting structures resembling those of the Cryphonectriaceae on trees in the Myrtales in Namibia, South Africa, Swaziland and Zambia. These fungi were identified with morphological characteristics and DNA sequence data. For the first time we report Chrysoporthe austroafricana from Namibia and on Syzygium guineense and Holocryphia eucalypti in Swaziland on a Eucalyptus grandis clone. The host and geographic ranges of Celoporthe dispersa are expanded to include S. legatti in South Africa and S. guineense in Zambia. In addition a monotypic genus, Latruncellus aurorae gen. sp. nov., is described from Galpinia transvaalica (Lythraceae, Myrtales) in Swaziland. The present and other recent studies clearly emphasize the limited understanding of the diversity and distribution of fungi in the Cryphonectriaceae in Africa.University of Pretoria (UP), National Research Foundation (NRF), Forestry and Agricultural Biotechnology Institute (FABI), Tree Protection Cooperative Program (TPCP

The Eucalyptus canker pathogen Holocryphia eucalypti on Eucalyptus in New Zealand

Holocryphia eucalypti is an opportunistic canker pathogen of Eucalyptus and Corymbia spp. (Myrtaceae, Myrtales) in Australia and South Africa. It is also known in Australia on Tibouchina trees (Melastomataceae, Myrtales). Using DNA sequence comparisons and morphological characterisation, we show for the first time that H. eucalypti is present in New Zealand on Eucalyptus spp.National Research Foundation (NRF), members of the Tree Protection Co-operative Program (TPCP), THRIP support program of the Department of Trade and Industry, Department of Science and Technology/National Research Foundation Centre of Excellence in Tree Health Biotechnology (CTHB

Fusarium casha sp. nov. and F. curculicola sp. nov. in the Fusarium fujikuroi Species Complex Isolated from Amaranthuscruentus and Three Weevil Species in South Africa

Trials are currently being conducted in South Africa to establish Amaranthus cruentus as a new pseudocereal crop. During recent surveys, Fusarium species were associated with weevil damage in A. cruentus fields. Preliminary studies showed that some of these Fusarium species grouped into two distinct clades within the F. fujikuroi species complex. The aim of this study was to characterize these isolates based on the morphology and phylogeny of the translation elongation factor 1α (TEF1α) gene region, ß-tubulin 2 (ßT) gene region and RNA polymerase II subunit (RPB2), and to determine if these isolates are pathogenic to A. cruentus. Phylogenetic and morphological studies showed that these two clades represent two novel species described here as F. casha and F. curculicola. Both species were shown to have the potential to be pathogenic to A. cruentus during routine greenhouse inoculation tests. While isolations indicate a possible association between these two species and weevils, further research is needed to understand this association and the role of weevils in disease development involving F. casha and F. curculicola in A. cruentus

Comparison of procedures to evaluate the pathogenicity of Ceratocystis fimbriata sensu lato isolates from Eucalyptus in South Africa

Ceratocystis fimbriata sensu lato (s.l.) is an important pathogen of Eucalyptus. Pathogenicity of isolates has typically been evaluated by inoculating seedlings under greenhouse conditions. It is, however, not clear how accurately this reflects pathogenicity under field conditions. In this study, five techniques to potentially screen C. fimbriata isolates for their relative pathogenicity to Eucalyptus were compared. These included: in vitro growth comparisons on artificial media; inoculations on apples; inoculation on Eucalyptus seedlings in a greenhouse; inoculations on Eucalyptus bolts freshly cut from stems of young trees; and field inoculations on young trees. Eight isolates of C. fimbriata s.l. collected from various areas in South Africa were used. There was considerable variation in growth in culture and aggressiveness of the eight isolates. Field inoculations on young trees were best correlated with inoculations of bolts (r = 0.76). Lower correlation coefficients were obtained with seedlings (r = 0.59), apple inoculations (r = 0.56), and in vitro colony growth (r = 0.42). Inoculation of bolts provides a rapid and reliable method to screen isolates of C. fimbriata s.l. for pathogenicity to Eucalyptus.National Research Foundation (NRF), members of the Tree Protection Co-operative Programme (TPCP), THRIP initiative of the Department of Trade and Industry